The invention relates to an appliance for introducing liquid and/or gaseous inert gas into a liquid extinguishing medium, essentially consisting of an extinguishing line provided with extinguishing nozzles, into which extinguishing line an extinguishant supply line provided with a non-return valve opens, and into which extinguishing line a supply tube opens for the liquid and/or gaseous inert gas, which supply tube is provided with a metering valve.
The introduction of liquid and/or gaseous inert gas into a liquid extinguishing medium is sufficiently known:
An appliance is described in WO-95/24274 in which the gaseous inert gas additionally acts as the driving agent for the extinguishant. The inert gas is introduced to the mixing appliance intermittently and, in fact, in a quite definite quantity in order to achieve a defined plug flow with separated gas and water parts in the feed line to the extinguishing nozzle. The flow emerging from the extinguishing nozzle is subjected to an acoustic field whose frequency is a multiple of the frequency of the plug flow within the feed line.
A further known solution for manual fire extinguishers in accordance with DE-U1 295 10 982 provides for CO2 to be supplied to the extinguishant at the extinguishing nozzle itself. This is intended to generate a homogeneous aerosol-type water mist jet with water droplets brought down to freezing temperature.
Also known from WO-95/28204 or WO-95/28205 are mixing appliances in which the gaseous inert gas is likewise used as the driving agent for the extinguishant. The object of these appliances is an effective mixing without delay of the gas with the extinguishing fluid. This mixture then flows via a line to the extinguishing nozzles which are arranged downstream in series. Tests have shown that, in such an arrangement, the pressure in the system immediately collapses as soon as the gas-containing extinguishant acts on the first extinguishing nozzle. The result of this is that the extinguishing nozzles located downstream are no longer adequately supplied with extinguishant.
EP-A-0 798 019 describes a method and an appliance in which a liquid inert gas is supplied under increased pressure to the extinguishant in order to generate a two-phase bubble flow. For this purpose, more inert gas is supplied than can go into solution under the given pressure relationships and the residence time selected. An aerosol with optimum droplet size for combating fire appears at the extinguishing nozzle.
Tests have shown that, in the appliance in accordance with EP-A-0 798 019, the surplus inert gas reseparates after a certain time from the extinguishant in the pipework. Help is provided in this case by a subsequent mixing appliance, such as is known from EP-A-0 904 806 and in which an extinguishant which is oversaturated with inert gas is again generated. The injection means, which can be radial holes, in the case of the mixing appliance in accordance with EP-A-0 904 806 are dimensioned in such a way that a homogeneous fine distribution of the gas with the smallest possible gas bubbles has been achieved in the water on injection of the inert gas into the duct through which the extinguishant is flowing. In this arrangement, however, it is necessary to ensure that the nozzle holes are, in turn, large enough to reliably avoid freezing of the openings. In order to form a defined bubble flow downstream of the injection, more CO2 is introduced into the extinguishant than can go into solution. The excess proportion which is not dissolved is present in the form of bubbles. Depending on the respective pressure and temperature, the mixture has a tendency to evaporate; a pressure loss in the line will therefore cause evaporation. Compensation is provided for part of the pressure drop by degassing the dissolved inert gas. The evaporation causes an increase in volume. This measure at least achieves advantageous retention of pressure, as has been found by tests. In the end, this means that all the extinguishing nozzles are subjected to approximately the same extinguishing pressure, independently of the associated line length. In the case of excessively large holes in the injection means, however, the desired homogeneous fine distribution of the gas, as already mentioned at the beginning, cannot be achieved in the water. In order to provide help on this point, means which influence the flowxe2x80x94in the form of vortex generatorsxe2x80x94are arranged in the duct through which flow occurs. These vortex generators are arranged in such a way that a sufficiently large mixing zone is available downstream of them within the casing. These means which influence the flow can also be provided again further downstream if the inert gas surplus begins to separate from the extinguishant.
The invention is based on the object of creating an appliance, of the type mentioned at the beginning, in which all the extinguishing nozzles are supplied with extinguishant of sufficient pressure, while avoiding auxiliary means which influence the flow.
In accordance with the invention, this is achieved by the supply tube merging into a perforated distributor body within the extinguishing line, which distributor body extends along the extinguishing line, and in which arrangement at least one hole is arranged in the distributor body between each two sequential extinguishing nozzles in the flow direction of the extinguishing medium in the extinguishing line.
The advantages of the invention may be seen, inter alia, in the particular simplicity of the measure. The appliance is very effective at a given low water pressure. The extinguishing system upstream of the non-return valve can be designed for the 16 bar which is suitable for fire protection, whereas the system downstream of the non-return valve has to be dimensioned to average pressures in the region of approximately 40 bar. The increased pressure level relative to conventional low-pressure systems has, in consequence, an increased extinguishing performancexe2x80x94inter alia because of the attainable finer atomization with a simultaneously increased projection distance. The quantity of extinguishant can be massively reduced due to the cyclic operation possibility provided. Because the pressure is not introduced into the system upstream, but in the immediate vicinity of the extinguishing nozzles, the system reacts with extraordinary rapidity. Multiple connection locations are dispensed with because the distributor body is now arranged within the extinguishing line.
It is particularly advantageous for the distributor body to be a flexible hose. Such a distributor body can be adapted without difficulty to any possible geometry of the extinguishing line.
An obvious possibility is to employ a high-pressure plastic hose as the flexible distributor body. Such a commercial product, for pressures up to 90 bar for example, is easily processed. The use of plastic, furthermore, eases the problem of icing when the liquid inert gas enters the extinguishant and, by this means, simplifies the choice of the size and number of the holes in the distributor body.
It is expedient for the center lines of the extinguishing nozzles in the extinguishing line to be directed at least approximately parallel to the potential fire surface. A so-called spatial protection can be effected by this means. In the previously usual, essentially vertical, spraying of the fire surface, it is generally necessary to spray against the thermal current of the flame. Because of this, it is difficult for the extinguishant to reach the actual source of the fire. The new parallel spray systemxe2x80x94in the case where a machine has to be protected, this is understood to mean that the center line of the spray cone extends essentially coaxially with the center line of the machinexe2x80x94is based less on the previously known cooling principle but, rather, on the suffocation principle. The idea is to simply blow the flame away by means of the extremely fine extinguishant mist. In this arrangement, the extinguishant is sprayed into the zone between the combustible and the flame.